Evaluating the Chemical Composition and Antitumor Activity of Origanum vulgare ssp. hirtum Essential Oil in a Preclinical Colon Cancer Model

<i>Origanum vulgare</i> ssp. <i>hirtum</i> is an aromatic plant native to various Mediterranean regions and has been traditionally used in folk medicine. This study investigates the chemical composition and the potential antitumor activity of its essential oil in a preclinical model of CT26 colorectal cancer in BALB/c mice. Mice received prophylactic oral administration of the essential oil, and tumor progression, immune modulation, and apoptosis were evaluated. Even treatment with low doses (350 parts per million, ppm in 100 μL final volume) of the essential oil significantly suppressed tumor growth by approximately 44%. This effect correlated with the enhanced expression of antitumorigenic cytokines, including a 2.7-fold increase in type I interferons (IFN), IFN-γ (from 46.5 to 111.9 pg/μL per mg of protein) and tumor necrosis factor alpha (TNF-α) (from 34.5 to 103 pg/μL per mg of protein). Furthermore, the production of granzyme B, a key mediator of cytotoxic immune cell function, was notably increased from 96.1 to 319.6 pg/μL per mg of protein. An elevated activation of caspase 3, a central effector caspase of all apoptotic cascades, was also observed in tumors from oregano-treated mice. These findings suggest that <i>O. vulgare</i> ssp. <i>hirtum</i> essential oil exhibits promising antitumor properties through immune modulation and immunity-mediated apoptosis induction, supporting its potential development as a bioactive compound for cancer prevention or therapy.